The present invention relates to a pattern collation apparatus for performing collation of N-dimensional patterns (e.g., fingerprints (two-dimensional) and stereoscopic (three-dimensional) patterns) on the basis of spatial frequency characteristics.
Fingerprint collation apparatuses have begun to replace apparatuses using personal identification numbers and ID cards in the fields demanding personal recognition such as the fields of the management of access to computer rooms and important mechanical rooms and the management of access to computer terminals and financial terminals in banks.
The present inventor proposed a pattern collation apparatus in Japanese Patent Application No. 7-108526. In this pattern collation apparatus, two-dimensional discrete Fourier transform is performed for the image data of registration patterns to generate registration Fourier image data, and two-dimensional discrete Fourier transform is performed for the image data of a collation pattern (subjected to collation) to generate collation Fourier image data. The registration Fourier image data and the collation fourier image data are synthesized. Two-dimensional discrete Fourier transform is then performed for the resultant synthesized Fourier image data, and n pixels having higher spectrum intensities are extracted from a correlation component area appearing in the synthesized Fourier transformed image data. The average of the spectrum intensities of the n extracted pixels is set as a correlation value. This correlation value is compared with a threshold. With this process, collation between the registration patterns and the collation pattern is performed.
In this pattern collation apparatus, however, if a rotation offset of six degrees or more occurs between a given registration pattern and a collation pattern, the registration pattern and the collation pattern cannot be identified as identical patterns or different patterns.